This invention relates to an assembly for collecting a liquid sample from a patient, such as a blood sample. More particularly, this invention relates to a needle assembly for collecting sequentially multiple liquid samples from such a patient. The device of the invention utilizes a receiving chamber with walls which are translucent or transparent for visually indicating whether or not proper access to the source of the sample in question has been achieved. Moreover, the housing or chamber which receives the sample incorporates therein a porous filter which filter is comprised of a material which provides, simultaneously, a liquid barrier for the sample received in the housing, and a gas displacement discharge passage for gas displaced by the liquid sample received in the chamber.
The filter in the housing is positioned in such a way that it extends from the chamber to an exit point for the discharge of gas out of the housing chamber, which exit point may be covered by the cooperative engagement of the flange of the rubber sleeve or valve means which extends over the discharge opening of the negative pressure cannula during periods when a sample is not being discharged therefrom into an evacuated tube. Subsequently, when a liquid sample is to be discharged into an evacuated tube placed over the negative pressure cannula, the stopper for the tube engages the sleeve in a conventional manner. The negative pressure point of the negative pressure cannula passes through the stopper of the evacuated tube and the stopper moves along the negative pressure cannula toward the housing. In doing so, the point of the negative pressure cannula pierces the sleeve, and causes the sleeve to collapse and move toward the adjacent housing face. Thus, the flange of the sleeve is caused to engage the housing face, closing off the exit end of the filter device. For this reason, when a sample is being collected from the housing chamber into an evacuated tube, no air is allowed to pass through the filter from outside into the chamber.
Once the evacuated tube is withdrawn from the negative pressure cannula, the sleeve moves outwardly to reseal the discharge opening of the negative pressure cannula and the sample chamber in the assembly housing until the next evacuated tube is inserted into the assembly. Thus, with the sequential application of a series of evacuated tubes, the tubes move the sleeve out of engagement with the negative pressure discharge opening or point of the negative pressure cannula, and cause the flange of the sleeve to engage the exit opening of the filter to prevent any air passing into the sample chamber.
As discussed above, it is desirable to provide a mechanism whereby the user of such a needle assembly can be informed when the intravenous needle has penetrated the vein of the patient for collecting a blood sample. Many times, in collecting blood from a patient, it is difficult to locate the vein, or for other reasons blood flow into the collecting device is not adequate. In those instances, it is advantageous to be able to make a quick determination that entry into the vein has been made and that blood is flowing into the needle assembly.
Once this determination has been made and the vein entry achieved, the evacuated blood collection containers can be inserted, sequentially, as discussed above, into the collection assembly in accordance with well known techniques of collecting blood samples during a single collection procedure. Thus, by utilizing a translucent or transparent chamber, with the assembly of the invention herein, the fact that blood flow has been obtained is quickly realized simply by the user visually noting blood collecting in the housing chamber of the assembly of the invention here. Furthermore, as discussed above, with the utilization of the porous filter in the housing wall, the filter allows for displacement of the air from the housing chamber so as to allow room for receiving the blood sample being collected.
A prior art device which recognizes the utilization of a porous material for providing a venting for displaced air during receiving a blood sample is taught in U.S. Pat. No. 4,207,870, issued June 17, 1980. That assembly requires a separate one-way valve construction which opens and allows blood to travel from the vein of the patient and through the housing and into an evacuated container. Other related applications include co-pending U.S. applications Ser. No. 160,781 filed June 18, 1980, now U.S. Pat. No. 4,340,068, issued July 20, 1982, Ser. No. 284,894 filed July 20, 1981 and Ser. No. 311,494 filed Oct. 15, 1981.
Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claims.